ICT equipment such as a server device is usually installed in an air-conditioned machine room and operated in a somewhat constant temperature condition (see Patent Document 1). Patent Document 1 discloses a technique of controlling temperature and humidity in a server case for storing a plurality of servers. To be specific, the disclosed technique is a technique of controlling the rotation number of a supply fan that flows the air into the server case, the rotation number of a return fan that flows the air within the server case to the outside, the quantity of control of a cooling coil, the quantity of control of a humidifier, and so on, based on outside air temperature detected by an outside air temperature sensor and outside air humidity detected by an outside air humidity sensor. However, in recent years, for the purpose of reducing the investment cost and operation cost for a machine room, a machine room in which the inside of ICT equipment is cooled down by outside air taken therein draws increasing attention. Because the indoor temperature of a machine room utilizing outside air varies more than that of an air-conditioned machine room, it is desirable to provide ICT equipment with a function of controlling the inside temperature thereof.
ICT equipment having an inside temperature control function is disclosed in Patent Document 2, for example. A server device disclosed in Patent Document 2 includes a cooling fan, an intake air temperature sensor that detects the temperature of intake air, a component temperature sensor that detects the temperature of an electronic component inside the device, and a control part that controls the rotation number of the cooling fan. The control part controls the rotation number of the fan based on the result of detection by the intake air temperature sensor and the result of detection by the component temperature sensor.
To be more specific, until the results of detection by all of the component temperature sensors become equal to or less than a first component temperature threshold, the control part compares the result of detection by the intake air temperature sensor with a plurality of intake air temperature thresholds set in advance, and rotates the cooling fan at the rotation number in accordance with the result of comparison (increases the rotation number as the intake air temperature is higher). When the results of detection by all of the component temperature sensors become equal to or less than the first component temperature threshold, the control part compares the results of detection by the component temperature sensors with second to fourth component temperature thresholds, and controls the rotation number of the cooling fan in the following manner based on the result of comparison.
In a case where the results of detection by all of the component temperature sensors are equal to or less than the second component temperature threshold (first component temperature threshold<second component temperature threshold), the control part gradually decreases the rotation number of the cooling fan. In a case where the results of detection by all of the component temperature sensors are higher than the second component temperature threshold and equal to or less than the third component temperature threshold (second component temperature threshold<third component temperature threshold), the control part keeps the current rotation number. In a case where the results of detection by all of the component temperature sensors are higher than the third component temperature threshold and equal to or less than the fourth component temperature threshold (third component temperature threshold<fourth component temperature threshold), the control part gradually increases the rotation number of the cooling fan. In a case where the results of detection by all of the component temperature sensors exceed the fourth component temperature threshold (third component temperature threshold<fourth component temperature threshold), the control part causes the cooling fan to rotate at a rotation number corresponding to the result of comparison between the result of detection by the intake air temperature sensor and the intake air temperature thresholds set in advance.
Patent Document 1: Japanese Unexamined Patent Application Publication No. JP-A 2011-242011
Patent Document 2: Japanese Unexamined Patent Application Publication No. JP-A 2011-151131
According to the technique disclosed in Patent Document 2, it is possible to cool the inside of ICT equipment without depending on a cooling system. However, because the technique disclosed in Patent Document 2 is designed to increase the rotation number of the cooling fan as intake air temperature becomes higher without considering intake air humidity, there is a fear that condensation occurs on the inner face of a case, the surface of a board, and so on, in a case where the temperature of intake air sharply rises.